Eclipses occur because the moon and Earth are always moving. Earth orbits, or goes around, the sun. And at the same time, the moon orbits Earth.
As Earth and the moon travel in their orbits, sometimes Earth moves between the sun and the moon and blocks the sunlight that normally reaches the moon. We call this an eclipse of the moon, or a lunar eclipse.
You can see a lunar eclipse only at night when the moon is full, but you won’t see one every time there’s a full moon. The moon’s orbit around Earth is tilted a little compared to Earth’s orbit around the sun. So Earth’s shadow usually misses the moon. But when the sun, Earth, and moon line up exactly right, the eclipsed moon will look reddish…
